The invention relates to optical readers in general and specifically to an optical reader imaging module which emits light in more than one visible color wavelength band.
Most image signal generating data collection devices require built-in illumination elements for illuminating a target area. The built in illumination elements and structural members supporting them consume substantial space. Laser scanner based imaging modules are becoming available in increasingly small sizes. The Symbol SE900 imaging module is an example of a small-sized laser based image imaging module. The face profile of the SE900 module is about 0.81xe2x80x3 wide (xe2x80x9cxxe2x80x9d)xc3x970.45xe2x80x3 high (xe2x80x9cyxe2x80x9d).
Certain problems have been noted with laser based imaging modules, however. First, laser based imaging modules are not well adapted to capture 2D images and therefore cannot be utilized in a system for decoding certain types of 2D indicia such as 2D matrix bar codes and OCR characters. Although existing laser based imaging modules read stacked 2D symbologies such as PDF417, they typically are not appropriate for the capture of 2D images. Attempts to adapt a laser scanner based image engine for 2D image capture have been unsuccessful. Laser scanning 2D image engines, while generating low resolution image signals, have been observed to be costly, and space consuming. Another major problem noted with laser based bar codes is their lack of durability. Laser scan engine modules require a moving mirror which is delicately mounted. Mirror mount structure can easily be misaligned or broken by sudden impact of a housing incorporating the module on a rigid object. The mechanical complexity of a laser scanner based imaging module increases significantly if the module must generate 2D image signals.
In spite of the significant problems relating to laser scanner imaging modules in their inability to read 2D indicia, and their fragility, some users of dataform reading instruments continue to be impressed with certain advantages that are exhibited by them. First, as mentioned, laser scanner based imaging modules, because of their limited functionality can easily be made in packages of reduced size and weight. Second, some users react positively to the neat and clean aiming and illumination pattern that is projected onto a target by a laser scanner based imaging module. Laser scanner based imaging modules project a collimated narrow beam of light onto a target. The beam is scanned to define an aiming line. Because the line is well defined, users can readily locate the scan line on an indicia to be read within a target area. The positioning of an imaging module aiming pattern is sometimes referred to as xe2x80x9csightingxe2x80x9d a target indicia.
It would be desirable to incorporate the size packaging and sighting advantages presently exhibited by laser scanner imaging modules into a highly durable image sensor based imaging module which exhibits the traditional performance and durability advantages of image sensor based imaging modules.
In accordance with its major aspects and broadly stated, the invention is an imaging module including a printed circuit board, an image sensor electrically connected to the printed circuit board, a support assembly for supporting at least one optical element, and an illumination system for generating an illumination pattern onto a target. The illumination system may include illumination light sources and diffusers for diffusing light from the illumination light sources. The module may further include an aiming system having an aiming light source, an aperture for stopping light from the aiming light source, and an optical element for projecting an aiming pattern into target area. For the reduction of the size of the module either or both of the illumination and aiming systems may include light redirecting elements such as mirrors or prisms.
In another aspect, the imaging module may include support posts for supporting various components of the imaging module. The module may include a first circuit board carrying an image sensor, a second circuit board carrying at least one light source, a support assembly interposed between the first and second circuit boards, and aligned post holes on each of the first circuit board, second circuit board, and support assembly for accommodating several support posts which, when accommodated in the post holes, support the structure including the support assembly interposed between two circuit boards. The support posts may be made electrically conductive so as to avoid a need to provide an additional electrical connector between the first and second circuit boards.
In another aspect, the imaging module may incorporate an aiming system including a light source, an aperture and an optical element positioned optically forward of the aperture wherein the aiming system projects a crisp and sharp aiming pattern onto a target over a wide range of distances. In one embodiment, an aiming system is configured so that a lens aperture effect results in a crisp sharp aiming pattern over a wide range of distances including distances at which the aiming pattern is less than optimally focused. In another embodiment an aiming system is configured so that light emanating from a thin aperture is imaged in such a manner that a crisp, sharp aiming pattern is defined over a wide range of distances. The aiming pattern in one embodiment includes sharply defined lateral edges which are useful in sighting target indicia.
In still another aspect, the module of the invention can include at least one multiple color emitting light source comprising a plurality of different colored LED dies each independently drivable so that the overall color emitted by the light source can be controlled and varied. The multiple color emitting light source can be controlled so that the color emitted by the light source is optimized for imaging or reading in a present application environment of the module. Further, the module can be configured so that control of the multiple color emitting light source automatically varies depending on a sensed condition, such a color present in a field of view of the module, the distance of the module to a target, and/or a predetermined criteria being met so that feedback is provided to a user. The module in a further aspect can include illumination light sources and aiming light sources which project light in different wavelength emission bands.
With the substantial size reductions made possible with architectures according to the invention, the positioning between a lens assembly and an image sensor can significantly affect the performance of the module. Accordingly, an imaging module in accordance with the invention may be adapted so that a position of a lens assembly can be finely adjusted relative to a position of an image sensor. A retainer and lens assembly according to the invention are complimentarily configured so that the lens assembly is slidably received in the retainer. The retainer includes two apertures defined in sidewalls thereof. The first aperture accommodates a fixture pin for use in finely adjusting the position of the lens assembly within the retainer. The second aperture accommodates an adhesive material for adhesively bonding the lens assembly to the retainer. Adhesive material may further be applied in the first aperture.
In a still further aspect of the invention, a module according to the invention can include aiming and illumination light sources having improved architectures. Light sources incorporated in the module can include surface integrated LEDs in which part of the light source is defined by a printed circuit board. Use of surface integrated LEDs in a module appropriately configures substantially reduces a dimension of the module in at least one plane. The module can also incorporate side leaded surface mount LEDs which can be firmly benched against a printed circuit board to achieve precision alignment of the LEDs without additional aligning members or alignment aiding assembly steps.
In yet another aspect of the invention, a module according to the invention can include one or more heat sink structures for reducing a temperature of the module. In another aspect, support posts of the module are utilized for purposes other than structurally supporting and electrically connecting members of the module. The support posts can be utilized to attach additional structural members (e.g. PCBs, optical plates, heat sink structures) which can be considered part of the module when they are attached. The support posts can also be utilized in mounting, supporting, or stabilizing the module in a housing interior member or on another member on which the module may be attached. The module may further include an xe2x80x9cunpackagedxe2x80x9d image sensor which is manufactured to be devoid of at least one of its traditional components so that a further size reduction of the module is realized. In a still further aspect of the module, the module may include a flexible circuit board so that the shape of the module can be varied, rendering the module fittable into a variety of cavity configurations. The module can also include light pipes for directing light from a light source into a target area.
With the significant miniaturization achievable with module architectures according to the invention, the module can readily be fittable into instrument or device housings of small size which become optical readers with the module installed therein. Modules according to the invention can be installed for example in gun style reader housings, personal data assistants (PDAs), portable data terminals (PDTs), mobile telephones, calculators, wrist watches, finger worn xe2x80x9cring scanners,xe2x80x9d writing implements such as pens, and numerous other devices.
These and other aspects of the invention will be described in further detail herein with reference to the below listed drawings, and detailed description of the invention.